1. Technical Field
The present invention provides a system and method for managing data updates in a hierarchy of virtual copies of data. More specifically, the present invention provides a mechanism for cascading changes to a data track to child copies of metadata pointing to the changed data track.
2. Description of Related Art
In known storage subsystems that make use of instant copy operations, such as the Snapshot instant copy mechanism available from Storage Technology, Inc., data files are received from a processor and stored in back-end data storage devices by mapping the processor assigned data file identifier to a logical address that identifies the physical storage location of the data. This mapping allows instant copies of data files by creating duplicate data file pointers that reference the original data files. In this dynamically mapped virtual data storage system, the data files are referred to as a collection of “virtual tracks” and each data file is identified by unique virtual track addresses (VTAs). More information about the Snapshot instant copy mechanism may be found in the incorporated U.S. patent application Ser. No. 09/884,822 entitled “APPARATUS AND METHOD FOR INSTANT COPY OF DATA.”
Using an instant copy mechanism, such as the Snapshot instant copy mechanism, may result in many copies of the same set of metadata entries, i.e. a subset of the metadata table, being used in a storage subsystem. It is useful to manage these various copies of the metadata so that changes to data tracks associated with metadata entries are passed along to appropriate copies of the metadata. Thus, it would be beneficial to have a system and method for managing data updates in systems where virtual copies of data are created through an instant copy operation.